We are investigating the photobleaching dynamics of molecules under pulsed laser excitation. A steady state theory has been developed which incorporates molecular diffusion as well as the possibility of nonlinear bleaching rates. An analysis of preliminary results with Rhodamine B in various solvents suggests that, while molecular fluorescence scales as a 2-photon process, molecular photobleaching can scale as a 3-4 photon process, suggesting possible improvements in the design of a nonlinear microscope so as to minimize photodamage.